1. Field of the Invention
The present invention relates to an L-glutamine producing bacterium belonging to coryneform bacteria and a method for producing L-glutamine. L-Glutamine is an industrially useful amino acid as an ingredient of seasonings, liver function promoting agents, amino acid transfusions, comprehensive amino acid preparations and so forth.
2. Related Art
In order to produce L-amino acids by fermentation, methods for improving microorganisms by breeding have been used abundantly. That is, since production ability of wild strains per se for L-amino acid production is extremely low in many cases, there have been known methods of imparting auxotrophy or analogue resistance by mutation or imparting mutation for metabolic regulation and methods utilizing a combination of these. Although L-glutamine can be obtained with an appropriate yield by the aforementioned methods, it is indispensable to further improve the fermentation yield in order to industrially produce L-glutamine at a low cost.
Further, the L-glutamine fermentation also suffers from the problem of by-production of L-glutamic acid. A method for solving this problem is proposed in, for example, Japanese Patent Laid-open Publication (Kokai) No. 3-232497. Although the production of L-glutamic acid can be suppressed to a certain extent by this method, there is still by-production of L-glutamic acid and the yield of L-glutamine is insufficient.
Since such improvements of L-glutamine producing bacteria as mentioned above utilize methods of treating a host bacterium with a mutagenizing agent or the like and selecting a strain showing improved productivity for L-glutamine from bacteria randomly incorporated with mutations, they require much labor and suffer from difficulties.